1. Field of the Invention
The present invention pertains to methods and apparatus for producing powders. More particularly, the present invention relates to techniques for producing metal or metal-alloy oxide powders by combustion.
2. Description of Prior Art
Metal oxide powders find use in chemical laboratories and in manufacturing processes. Various techniques are available for manufacturing oxides, depending on the oxide to be produced. Such techniques include reduction of ores, vaporizing metals in air followed by oxidation of the metal vapor, burning compounds that are flammable in air, and various processes involving roasting, leaching, purification and/or precipitation, for example. U.S. Pat. No. 5,114,702 issued May 19, 1992, discusses a technique for making metal oxide ceramic powders by forming an aqueous solution of a metal salt and a combustible co-reactant compound such as an amino acid, allowing the excess water to evaporate, and heating the resulting concentrated material to its autoignition temperature.
Existing methods for producing metal oxide powders generally comprise multistep processes requiring elaborate apparatus, and are relatively time consuming, expensive and cumbersome. It would be advantageous and desirable to be able to produce large amounts of metal and metal-alloy oxide powders with a minimal number of process steps. The present invention provides a technique for so producing oxide powders utilizing combustion of the metal or metal alloy of which an oxide is to be produced.
U.S. Pat. No. 3,992,138 issued Nov. 16, 1976, discloses a particular construction of a combustion chamber. U.S. Pat. No. 3,975,184 issued Aug. 17, 1976, discloses method and apparatus for producing metallic powders using an electric arc furnace. U.S. Pat. No. 4,374,075 issued Feb. 15, 1983, is directed to a method of producing atomized particles of metals and alloys by use of a plasma arc gas jet. U.S. Pat. No. 4,964,791 issued Oct. 23, 1990, discloses apparatus for making powder in a hermetically sealed container using a plasma torch.
A combustion chamber is disclosed in U.S. Pat. No. 4,990,312 issued Feb. 5, 1991, and naming as a joint inventor one of the joint inventors of the present invention. The disclosure of the U.S. Pat. No. 4,990,312 is directed to testing apparatus for evaluating materials for exposure to high pressure gases, including inert or oxidizing gases.